Maybe it's better that a person with a gp2x answers this
, but a quick rundown of the two major problems:
The cap seems unergonomical, it's convex and people slip and some even get soars.
There is some solutions to this as the cap pops of easily and can be replaced, for example DaveC's replacement cap (just search for it)
The other problem is that for some reason it's designed with larger diagonal zones than orthogonal(?), this means it's easier to hit diagonals than up/down, right/left, and apparently makes some games close to unplayable.
This other problem is way harder to adress, and apart from software fixes (i.e. make some diagonals register as orthogonals) there are no solutions to this.
There have been some rumours about GPH acknowledging joystick problems and have said to adress them, but no hard facts on this.
this from the gp2x.com site
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2069 re admin 2006-01-20 230
it is actually Dpad.
but it is not designed well.
We are planning to make and sell or give better one for replacement
EDIT: yes i'm slow